Method for forming a connector assembly for use with an implantable medical device

ABSTRACT

A sectional interconnect ribbon for use in a connector assembly for an implantable medical device is formed of two ore more separately-formed sections which are mechanically joined together to form an integral assembly. The sectional interconnect ribbon, as well as at least one connection element, is embedded within the connector assembly.

BACKGROUND OF THE INVENTION

Some of the embodiments of the present invention relate generally to thefield of implantable medical devices, and more particularly, to a methodfor forming a connector assembly having a sectional interconnect ribbonembedded therein for use with an implantable medical device.

Implantable medical devices (IMDs) are becoming increasingly prevalentfor the treatment of a wide variety of medical conditions. For example,cardiac pacemakers and implantable cardioverter-defibrillators have beendeveloped for maintaining a desired heart rate during episodes ofbradycardia and/or for applying cardioversion or defibrillationtherapies to the heart upon detection of serious arrhythmias. Inaddition, tissue-stimulating IMDs are known for stimulating variousnerves, muscles and organs to treat a variety of conditions.

Most IMDs include a hermetically-sealed housing that encloses a powersource and electronic circuitry, at least one medical lead that bears atleast one electrode and/or sensor, and a connector assembly (sometimesreferred to as a header or block assembly) that electrically andmechanically couples the electronic circuitry in the housing to theelectrodes and/or sensors via the medical leads. The specific electroniccircuitry and lead configuration of the IMD depend upon the desiredfunctionality of the IMD (i.e., whether it is a pacemaker, a nervestimulator, or some other medical device).

Because the IMD housing is hermetically sealed, the medical leadspreferably do not penetrate the housing, but rather are coupled toelectrical connectors located within the connector assembly. To allowelectrical signals to pass between the electronic circuitry of the IMDhousing and the sensors and/or electrodes carried by the medical leads,the IMD housing is conventionally configured with feed-throughconductors located on its outside surface yet electrically coupled toits internal circuitry. Once the connector assembly is physicallyattached to the IMD housing, the pass-through conductors are routed fromthe IMD housing to one of the conductors of the connector assembly. Thepass-through conductors are then covered with a medical adhesive, andthe adhesive is cured to form a protective, insulating layer thatisolates the wires from external elements. Although this method isrelatively straight forward, it requires manual routing of theconductors and application of the adhesive, which in turn introducesundesired variables into the manufacturing process.

An alternative approach to the use of adhesives involves the positioningof one or more conductors within a mold in a predetermined orientation.An insulating material is then injected into the mold to encapsulate theconductors. While this process eliminates the variables associated witha manual step, it is nevertheless difficult to implement with other thana simple design. This is because the introduction of the plastic intothe mold at high pressures generally causes the position of theconductors to shift. Accordingly, in the molding process, shorts mayform between conductors, or conversely, a desired electrical connectionmay be lost. While injection molding systems of this type generallyinclude mechanisms to hold the conductors in place during the injectionprocess, the components may shift regardless of efforts to prevent suchshifting. Additionally, the difficulty associated with maintainingisolation between multiple conductors places limits on the assemblydimensions. That is, an assembly cannot be made too small because shortsare more likely to occur between closely spaced conductors that shiftduring the injection molding process. This may lead to a higher scraprate than would otherwise exist.

U.S. Pat. No. 6,817,905 (which is hereby incorporated, in relevantparts, by reference) improves upon this method with the introduction ofa two-shot method of forming a connector assembly. This method allowsfor the electrical conductors to be embedded within the connectorassembly while reducing the likelihood of the electrical conductorsshifting positions during the manufacturing process. According to thismethod, a core is formed of a first insulating material during a firstinjection molding step. The core is then loaded with various electricalconnector elements. Next, the electrical conductors are secured to thecore and are attached to a desired one of the electrical connectorelements. In one embodiment, the electrical conductors are formed as acircuit assembly (i.e., an interconnect ribbon) that can be handled as asingle unit during the assembly process. The circuit assembly may bestamped, or otherwise formed, from a single planar sheet of conductivematerial and then shaped for attachment to the core. In alternateembodiments, the electrical conductors are (1) individually loaded ontothe core, (2) joined in a single circuit member via insulated material,or (3) integrally formed with the electrical connector elements.

In a second injection molding step, the electrical conductors (exceptfor the electrical conductor pads), electrical connector elements, andthe core are overmolded with a second insulating material. Theelectrical conductor pads are then separated, both electrically andmechanically, from each other.

BRIEF SUMMARY OF THE INVENTION

Some of the embodiments of the present invention relate to a sectionalinterconnect ribbon for use in a connector assembly for an implantablemedical device. The sectional interconnect ribbon is formed of two ormore separately-formed sections which are mechanically joined togetherto form an integral assembly. The sectional interconnect ribbon, as wellas at least one connection element, is embedded within connectorassembly.

During fabrication of the connector assembly, a core portion is formedon to which the at least one connection element is loaded. The sectionalinterconnect ribbon is then attached to the at least one connectionelement. Next, a structure is formed that extends over and adheres to atleast a portion of the core element and to at least a portion of thesectional interconnect ribbon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an implantable medical device having aconnector assembly in accord with the present invention.

FIG. 2 is a perspective view of a core portion of the connectorassembly.

FIG. 3 is a perspective view of the core portion as loaded with variousconnector elements and a sectional interconnect ribbon in accord withthe present invention.

FIG. 4 is a bottom view of the loaded core portion illustratingelectrical connections between the various connector elements and thesectional interconnect ribbon.

FIG. 5 is a perspective view of the sectional interconnect ribbon afterit has been shaped to conform to the core portion.

FIG. 6 illustrates the sectional interconnect ribbon prior to beingshaped to conform to the core element.

FIGS. 7-8 illustrate first and second sections, respectively, of theinterconnect ribbon.

FIG. 9 is an exploded perspective view of the implantable medicaldevice.

DETAILED DESCRIPTION

As will be described in greater detail below, the present inventionprimarily discloses embodiments relating to a sectional interconnectribbon for use in a connector assembly for an implantable medical device(IMD). In designing a connector assembly, the number and configurationof both electrical connector elements and conductors may require aninterconnect ribbon design that simply cannot be stamped, or otherwiseformed, as a single unit from a planar sheet of conductive material. Inthese scenarios, the present invention provides a method and anapparatus for strategically dividing the interconnect ribbon intomultiple interconnect ribbon pieces that can be assembled into a singleunit to allow for a more efficient and less error-prone assemblyprocess.

FIG. 1 is a perspective view of implantable medical device (IMD) 20having housing 22, medical leads 24, and connector assembly 26.Implantable medical device 10 may be a cardiac pacemaker,cardioverter/defibrillator, a nerve stimulator, or any other type ofmedical device utilizing medical electrical leads 24. Housing 22 is ahermetically-sealed enclosure (or can) that houses a power supply andelectronic circuitry. The function and composition of this electroniccircuitry will vary depending upon the intended function of IMD 20.Housing 22 further includes pass-through connectors 28 to enable theelectronic circuitry housed therein to communicate with medical leads 24plugged into connector assembly 26 (sometimes referred to as a header orblock assembly). Medical leads 24 typically include, for example, atrialand ventricular pacing/sensing leads and subcutaneous leads. Each leadmay carry at least one electrode and/or sensor (not shown).

FIG. 2 is a perspective view of core portion 30 of connector assembly26. Core portion 30 is shaped to support various metal parts in a stablemanner that can be maintained during an overmolding process to bediscussed below. The specific shape of core portion 30, however, will bedictated by the number and types of conductive elements to be embeddedin conductor assembly 26, the desired final shape of conductor assembly26, and various other design considerations. For example, in theembodiment shown in FIG. 2, core portion 30 includes receptacles 32 and34, each of which is adapted to receive a set-screw block, andreceptacles 36 and 38, each of which is adapted to receive an electricalconnector bore. Additionally, core portion 30 includes channels 40 alongan external surface thereof for guiding the placement of electricalconductors.

Core portion 30 preferably is formed of a biocompatible thermoplasticmaterial, such as, for example, without limitation, polyurethane. In oneembodiment, core portion 30 is formed by heating the thermoplasticmaterial to a temperature that is at, or slightly above, its melt point.The material is then injected into a primary mold and allowed to cool.After cooling, core portion 30 is removed from the mold. In an alternateembodiment, core portion 30 may be fabricated via a machining process.

FIG. 3 is a perspective view of core portion 30 of connector assembly 26loaded with set-screw blocks 42 and 44, electrical connector bores 46and 48, and sectional interconnect ribbon 50. At this stage of assembly,set-screw blocks 42 and 44 and electrical connector bores 46 and 48 arepositioned loosely in receptacles 32, 34, 36, and 38, respectively.Set-screw blocks 42 and 44 and electrical connector bores 46 and 48 maybe formed entirely, or partially of a conductive material, such asMP35N, stainless steel, or titanium. As is known in the art, set-screws42 and 44 are used in conjunction with electrical connector bores 46 and48 to electrically and mechanically couple to and secure in positionproximal ends of medical leads 24. As shown in FIG. 3, electricalconnector bore 46 conforms to an IS-1 standard for IMDs and electricalconnector bore 48 conforms to an IS-4 standard. In alternateembodiments, the number and types of electrical connector elements mayvary.

After core portion 30 has been loaded with these connector elements,sectional interconnect ribbon 50 is secured to the assembly. Forexample, sectional interconnect ribbon 50 is formed of a conductivematerial such as stainless steel, titanium, niobium, tantalum, or anyother biocompatible conductive material. Interconnect ribbon 50 includesmultiple traces or finger elements 52, 54, 56, 58, 60, and 62. At thisstage of the assembly, finger elements 52-62 are mechanically andelectrically joined together at tie bar portion 64 of sectionalinterconnect ribbon 50. This enables a more efficient and lesserror-prone assembly process because multiple elements need not beloaded individually onto core portion 30. Further, the likelihood offinger elements 52-62 shifting with respect to each other is reduced byhaving them formed in single interconnect ribbon 50.

Finger elements 52-62 of sectional interconnect ribbon 50 are adapted tobe placed externally on a surface of core portion 30. As describedabove, core portion 30 includes channels 40 for guiding some of fingerelements 52-62 into a desired position along the surface of core portion30. In alternate embodiments, core portion 30 may include aperturesthrough which some or all of finger elements 52-62 may be threaded.

FIG. 4 is a bottom view of loaded core portion 30 illustratingelectrical connections from sectional interconnect ribbon 50 toset-screw blocks 42 and 44 and electrical connector bores 46 and 48. Inone manner of use, finger elements 52-62 are initially straight, and maybe manually or automatically bent in the manner shown in FIGS. 3 and 4.In other embodiments, finger elements 52-62 are formed of a materialthat is deformable, and which may be temporarily straightened to beloaded onto core portion 30.

After sectional interconnect ribbon 50 is coupled to core portion 30, itmay be soldered, welded, or otherwise attached to form predeterminedelectrical and mechanical connections between connector members andset-screw blocks and respective ones of the conductive finger elements.In the embodiment illustrated in FIG. 4, as denoted by asterisks,set-screw block 42 is welded to finger element 58; set-screw block 44 iswelded to finger element 56; electrical connector bore 46 is welded tofinger element 60; and electrical connector bore 48 is welded to fingerelements 52, 54, and 62.

FIG. 5 is a perspective view of sectional interconnect ribbon 50 asshaped to conform to core element 30. In this example, the arrangementof finger elements 52-62 is dictated by a specific configuration ofset-screw blocks 42 and 44 and electrical connector bores 46 and 48, aswell as the assigned electrical connections of each of finger elements52-62 (as in turn dictated by the circuitry embedded within IMD housing22).

FIG. 6 illustrates sectional interconnect ribbon 50 prior to beingshaped to conform to core element 30. As is evident in this figure,interconnect ribbon 50 cannot be formed as a single unit from a planarsheet of conductive material because finger element 58 overlaps fingerelements 52 and 54 and finger element 60 overlaps finger elements 52,54, and 62. While it may have been possible to have reconfigured some ofthe connector elements and/or rearranged the assigned electricalconnections of some of finger elements 52-62, this proposition wouldlikely have significant redesign work. The present invention insteadstrategically divides interconnect ribbon 50 into first and secondsections 66 and 68, each of which can be separately formed from planarsheets of conductive material and then subsequently assembled into asingle unit. Thus, the present invention allows the technique of U.S.Pat. No. 6,819,905 to be used while accommodating designs that may beinconsistent with the interconnect ribbon being stamped from a singleplanar sheet. That is, the present invention gives the designer of theconnector assembly greater freedom.

FIGS. 7 and 8 illustrate first and second sections 66 and 68,respectively, of the interconnect ribbon 50. Section 66 includes fingerelements 52, 54, 56, and 62, while section 68 includes finger elements58 and 60. Each of sections 66 and 68 is stamped from a planar sheet ofconductive metal. Sections 66 and 68 are then assembled into a singleunit for ease of handling. In particular, section 68 fits between fingerelements 56 and 62 of section 66. In the embodiment illustrated in FIGS.5-8, section 66 includes a sub-portion 70 of tie-bar portion 64 to whichtie-bar portion 64 of section 68 is welded, soldered, or otherwiseconnected.

Each of finger elements 52-62 includes a connection pad 52 a-62 aintended for electrical and mechanical connection to pass-throughconnectors 58 of IMD housing 22. In this embodiment, each of connectorpads 52 a-62 a resides in a single plane. Other embodiments, however,may demand a different configuration of its connector pads, as well as adifferent number and arrangement of finger elements. In the embodimentillustrated in FIGS. 5-8, tie-bar portion 64 of section 68 is bent tomove connector pads 58 a and 60 a into the plane of connector pads 52 a,54 a, 56 a, and 62 a.

The addition of this bend can be avoided in alternate embodiments byshaping tie-bar portion 64 of section 68 to fit in gap 72 of section 66.Sections 66 and 68 may then be joined by lap welds along the seamsbetween sections 66 and 68 or by a supplemental tie-bar attached totie-bar portions 64 of both sections 66 and 68.

Turning back to the manufacture of connector assembly 26, once all ofthe connector elements have been inserted into core portion 30 andsectional interconnect ribbon has been attached thereto, the resultingcore assembly is then overmolded to form final connector 26. The processof preparing the core assembly for overmolding and the actualovermolding process are described in detail in U.S. Pat. No. 6,817,905,which is incorporated herein. In essence, however, this process involvesthe insertion of blocking elements into orifices of the connectorelements to prevent the orifices from being filled with moldingmaterial; the insertion of loaded core portion 30 into a second moldcavity, the heating of a biocompatible thermoplastic material to atemperature that is at, or slightly above, its melt point; the injectionof the heated thermoplastic material into the second mold; the coolingof the part; the ejection of newly-formed connector assembly 26 from themold cavity, and the removal of tie-bar portion 64 of sectionalinterconnect ribbon 50 to separate finger elements 52-62 from eachother.

FIG. 9 is an exploded perspective view of IMD 20 illustrating theattachment of connector assembly 26 to housing 22. Connector assembly 26and housing 22 include fastening elements 74 and 76, respectively, foraffixing connector assembly 26 to housing 22. Connection pads 52 a-62 aof finger elements 52-62 each connect with a respective one offeedthrough pins 28 of housing 22. To ensure connectivity, connectionpads 52 a-62 a are soldered, welded, or otherwise affixed to feedthroughpins 28. The area of these connections is then covered with a medicaladhesive.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, while the present invention hasbeen described above with reference to a two-step injection molding (orovermolding) process, the present invention is equally applicable toconnection assemblies formed via (1) a two-shot casting process, (2) atwo-shot injection molding process, (3) an injection molded first shotand a cast second shot process, and (4) a cast first shot and aninjection molded second shot process. Additionally, the first shot, orthe core portion, may be otherwise shaped or formed by a machiningprocess.

1. A method for fabricating a connector assembly for use in animplantable medical device, the method comprising: forming a coreportion; loading the core portion with at least one connection element;forming a first interconnect ribbon section comprising at least oneconductive finger element and a tie-bar portion, each finger elementhaving a free end for attachment to one of the electrical connectorelements and a fixed end attached to the tie-bar portion; forming asecond interconnect ribbon section comprising at least one conductivefinger element and a tie-bar portion, each finger element having a freeend for attachment to one of the electrical connector elements and afixed end attached to the tie-bar portion; joining the first and secondinterconnect ribbon sections into an integral interconnect ribbonassembly; attaching the integral interconnect ribbon assembly to thecore portion and the at least one connection element; and forming astructure that extends over and adheres to at least a portion of thecore element and at least a portion of the integral interconnect ribbonassembly.
 2. The method of claim 1 and further comprising: removing thetie-bar portion of the integral interconnect ribbon assembly such thateach of the finger elements of the integral interconnect ribbon ismechanically and electrically separated from one another.
 3. The methodof claim 1, wherein forming the first interconnect ribbon sectioncomprises: stamping the first interconnect ribbon section from asubstantially planar sheet of conductive material.
 4. The method ofclaim 3, wherein forming the second interconnect ribbon sectioncomprises: stamping the second interconnect ribbon section from asubstantially planar sheet of conductive material.
 5. The method ofclaim 1, wherein at least one of the conductive finger elements of thefirst interconnect ribbon section when laid flat overlaps at least oneof the conductive finger elements of the second interconnect ribbonsection when laid flat.
 6. The method of claim 1, wherein the fixed endsof the first and second interconnect ribbon sections have generallyplanar profiles that reside in substantially the same plane.
 7. Themethod of claim 1, wherein mechanically joining the first and secondinterconnect ribbon sections into an integral interconnect ribbonassembly comprises: lap welding the tie-bar portion of the firstinterconnect ribbon section to the tie-bar portion of the secondinterconnect ribbon section.
 8. The method of claim 1, whereinmechanically joining the first and second interconnect ribbon sectionsinto an integral interconnect ribbon assembly comprises: attaching asupplemental tie-bar to the tie-bar portions of the first and secondinterconnect ribbon sections.
 9. A connector assembly for use in animplantable medical device, the connector assembly being fabricated bythe method of claim
 2. 10. The connector assembly of claim 9, wherein atleast one of the conductive finger elements of the first interconnectribbon section when laid flat overlaps at least one of the conductivefinger elements of the second interconnect ribbon section when laidflat.
 11. The connector assembly of claim 9, wherein the fixed ends ofthe first and second interconnect ribbon sections have generally planarprofiles that reside in substantially the same plane.
 12. The connectorassembly of claim 9, wherein the tie-bar portions of the first andsecond interconnect ribbon sections are joined together via a lap weldjoint.
 13. The connector assembly of claim 9, wherein the tie-barportions of the first and second interconnect ribbon sections are joinedtogether via a supplemental tie-bar portion attached to the tie-barportions of the first and second interconnect ribbon sections.